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Equipment Discussions >> Mounts

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WadeH237
Pooh-Bah


Reged: 02/24/07

Loc: Snohomish, WA
Re: weird issue... new [Re: guyroch]
      #6319114 - 01/17/14 05:03 PM

Quote:

Quote:

Level makes no difference for polar alignment.




I disagree.

Guylain




Polar alignment is achieved when the mount's RA axis is perfectly parallel to Earth's rotational axis. It makes no difference at all whether the mount is level or not. It could be hanging upside down from a (very steady) tree branch and still be polar aligned if that criteria is met.

The process of getting the mount polar aligned can be made somewhat easier or more difficult, depending on whether the mount is level or not.

The reason for this is that your are adjusting the mount in altitude and azimuth. If the mount is perfectly level, a change in altitude does not affect azimuth and vice-versa. If the mount is not level, then a change in altitude will affect azimuth to some degree, and a change in azimuth will affect altitude to some degree.

This does not preclude you from achieving polar alignment. You either need to anticipate and account for the movement in the other axis, or you could do additional iterations of whatever method you are using to keep reducing the amount of error in the other adjustment.

It's this latter part that is the reason to get the mount level. But it's not an all or nothing deal. If the mount is reasonably close to level, then you'll have no problems. If the mount is leaning over 45 degrees, then you'll have a harder time of it.

I think that the main thing to remember is that there is not a whole lot to be gained by spending a huge amount of effort leveling the mount. Close is good enough.

This is especially true on a mount like the CG5 mentioned in this thread. The altitude and azimuth adjustments are so coarse, that it's impossible to make really tiny adjustments. I have many Celestron mount, including a couple of CG5s. I would say that it's impossible to get closer than say within 15 arc minutes of the NCP (unless you get lucky) just because of this.

Finally, everything that I've said here is really splitting hairs. For visual use, you can be a couple of degrees off the NCP and it won't result in problematic drift. Even for imaging, as long as you're guiding, you'll be fine with one iteration of ASPA.


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: weird issue... new [Re: guyroch]
      #6319117 - 01/17/14 05:06 PM

Quote:

Quote:

Level makes no difference for polar alignment.




I disagree.

Guylain




You can disagree all you want. A few minutes considering the geometry of the situations shows you are clearly wrong.


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: weird issue... new [Re: rmollise]
      #6319124 - 01/17/14 05:09 PM

I have been polar aligning the CG5 for years. It is more than possible to get the mount right on the money with the adjusters. I can easily get the AllStar star dead in the crosshairs of the Mallincam which yields fairly high "magnification." Similarly, it's no problem to drift align the mount to a point way closer than 15'...

The main caveat? Be careful tightening down the azimuth, as that can throw you back off.


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: weird issue... new [Re: Peter in Reno]
      #6319138 - 01/17/14 05:20 PM

Quote:



"It's kind of a yes and no answer that is rather subjective. To get a proper ASPA, you do not have to be perfectly level. This is where it gets somewhat subjective though. You can't get a good polar alignment out of a severely off balance tripod. The further away from level that you get, the worse your polar alignment will get. We've had many users in the past who will set up their tripod on a slight hill and not spend much time leveling the tripod and get great results. So it really depends alot of how off balance the tripod is."






I have no idea where this guy was going with the business about "off balance tripods." I don't see that this has much/anything to do with level. The only thing being level can do for you is make it a little easier to center the stars in some instances. That is all.


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WadeH237
Pooh-Bah


Reged: 02/24/07

Loc: Snohomish, WA
Re: weird issue... new [Re: rmollise]
      #6319172 - 01/17/14 05:36 PM

Quote:

I have been polar aligning the CG5 for years. It is more than possible to get the mount right on the money with the adjusters. I can easily get the AllStar star dead in the crosshairs of the Mallincam which yields fairly high "magnification." Similarly, it's no problem to drift align the mount to a point way closer than 15'...

The main caveat? Be careful tightening down the azimuth, as that can throw you back off.




You may be right. I was thinking about the CGE's azimuth adjustment, which is a pain to work with. Even when drift aligning the mount, it's really hard to get dialed in perfectly.

Still, even on the CG5, if I shutdown the mount and redo the 2+4 stars, then query the polar alignment, it shows errors typically in that neighborhood. I've never tried to drift align a CG5 to compare to what the hand controller reports.


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Peter in Reno
Postmaster
*****

Reged: 07/15/08

Loc: Reno, NV
Re: weird issue... new [Re: rmollise]
      #6319177 - 01/17/14 05:40 PM

This thread is about Celestron ASPA, not polar alignment in general (i.e. drift alignment where leveling mount is irrelevant). I am talking about ASPA on the FIRST TRY for a badly level mount. If you don't agree, kindly try this experiment yourself.

Celestron meant unlevel tripod/mount when they said off balance tripod because I mentioned unlevel mount when I sent them the message.

Peter

Edited by Peter in Reno (01/17/14 06:03 PM)


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: weird issue... new [Re: Peter in Reno]
      #6319203 - 01/17/14 06:07 PM

That's not what he said, however. He referred to "unbalanced" at least twice in his reply to you. I have _never_ found being off level to have any effect on go-to or ASPA alignment.

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Peter in Reno
Postmaster
*****

Reged: 07/15/08

Loc: Reno, NV
Re: weird issue... new [Re: rmollise]
      #6319218 - 01/17/14 06:24 PM

To all others, just level Celestron NexStar based mount as well as possible for ASPA to work well on the first try. It's not difficult to level the mount.

For interested reading about the thread regarding to ASPA and level mount, see:

ASPA and level

The conclusion is at (page 23) near the end of this incredibly long thread.

Peter


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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: Peter in Reno]
      #6319432 - 01/17/14 08:55 PM

Wow. Thread really expanded in the last few hours. First the bad news. Clouds. Not even a large mass. Just enough to make things difficult. The answe to my question is the star will hold while I center it. My yard is a slight incline so it should be workable. Thank you everyone. I hope the discussion continues. I am sure its helping others. :-)

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guyroch
Vendor (BackyardEOS)
*****

Reged: 01/22/08

Loc: Under the clouds!
Re: weird issue... new [Re: rmollise]
      #6319440 - 01/17/14 09:00 PM

Quote:

Quote:

Quote:

Level makes no difference for polar alignment.




I disagree.

Guylain




You can disagree all you want. A few minutes considering the geometry of the situations shows you are clearly wrong.




Well, if that is case Rod we will have to agree to disagree. I have no dog in this fight.

While technically leveling a GEM is not an absolute necessity, getting the mount setup as level as possible can save you time and frustration. A GEM can be out of level and still be polar aligned, once the R.A. axis is aligned and the declination axis set to the correct latitude the mount is correctly polar aligned, level or not. Once the mount is properly calibrated with ASPA it knows where the pole is and will perform good gotos, if not perfect most of the time. But for ASPA to tell the user how to adjust the mount in the first place it must start from a known geometry position, that position is a level mount. You can choose to ignore this, it makes to difference to me. I don't mean any disrespect by saying so, but you are wrong too. The initial geometry the mount assumes is a level mount, so saying the mount not needing to be levelled to polar align your mount is false; it does play a role!

I guess I do know a thing or two about geometry after all; sorry to disappoint you!

It is just that getting to the correct alignments when your GEM is out of level takes more time & work than starting out level. Leading a beginner in a direction where a level mount is irrelevant is not good advice IMO.

My 2 cents, and I'm out of this thread. It seems like simple advice of starting off with a level mount is used and twisted in ways that it was not intended to, that is too bad.

@wargrafix: Save yourself some time, trouble, frustration, and take the extra 2 minutes to start with your mount as level as possible. Two minutes is all it takes to remove a variable out of the equation that could lead to frustration.

Good luck!

Guylain


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TCW
professor emeritus


Reged: 11/05/13

Re: weird issue... new [Re: rmollise]
      #6319700 - 01/18/14 12:14 AM

How can leveling not help in accurate polar alignment? If your mount is set for your latitude then being out of level will guarantee it is not pointing at the pole even if it is pointing due north. The way I see it, it is a physical necessity. If it is not level then you would have to alter the latitude setting to point to the celestial pole.

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jrcrillyAdministrator
Refractor wienie no more
*****

Reged: 04/30/03

Loc: NE Ohio
Re: weird issue... new [Re: TCW]
      #6319717 - 01/18/14 12:29 AM

Quote:

If it is not level then you would have to alter the latitude setting to point to the celestial pole.




You always have to alter the elevation setting. Even if the base were perfectly level and the mount perfectly square (neither of which is possible) the latitude scale has nowhere near the resolution required to set the elevation with sufficient accuracy.


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TCW
professor emeritus


Reged: 11/05/13

Re: weird issue... new [Re: jrcrilly]
      #6319725 - 01/18/14 12:39 AM

The point is if you have an accurate latitude setting and the mount is level then all you have to do is change one plane to achieve alignment. Accurately leveling the mount only takes a few seconds if you use a decent level. Any latitude adjustment would be very small. As a builder I wince to hear someone say level makes no difference. Leveling should save time at the very least.

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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: weird issue... new [Re: TCW]
      #6320106 - 01/18/14 10:01 AM

There was a mile long thread on leveling for ASPA a while back that covered EVERY SINGLE aspect of it, I would refer all back to that.. I wonder if the OP got it working right, hopefully he will follow up, Kasey

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rmollise
Postmaster
*****

Reged: 07/06/07

Re: weird issue... new [Re: Peter in Reno]
      #6320178 - 01/18/14 10:47 AM

Quote:

To all others, just level Celestron NexStar based mount as well as possible for ASPA to work well on the first try. It's not difficult to level the mount.






Nope, but not necessary. If you are worried about level, level by eye is fine.

I've used the AllStar routine many times and have never given a moment's thought to leveling...and yet...AllStar works!

Edited by rmollise (01/18/14 10:56 AM)


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: weird issue... new [Re: guyroch]
      #6320180 - 01/18/14 10:49 AM

Quote:



I guess I do know a thing or two about geometry after all; sorry to disappoint you!




Maybe you do, maybe you don't. I have no way of knowing. If you do, you haven't thought this through very well.


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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: TCW]
      #6320210 - 01/18/14 11:01 AM

Tonight I hope the weather will cooperate. I agree levelling will certainly help but the slope is maybe 5 degrees so its not too bad. If I change the latitude scale if need be perhaps this will improve the accuracy. I guess the mechanical nature of these setups rely heavily on the levelling but if that isn't possible then workarounds need to be made.

Anyone every had the slew to target after doing a setup and pole alignment with no levelling still land not in the finder's cross hairs?


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John608
journeyman


Reged: 03/24/12

Loc: California
Re: weird issue... new [Re: wargrafix]
      #6320300 - 01/18/14 11:38 AM

Forget this issue of level it doesn't matter except that if you are on tilted ground you may want to adjust the tripod for it to keep your mount from being too easy to tip over on one side. Do the 2+4 alignment then do the ASPA making sure you follow the instructions in the manual. Your final moves to center your star will involve moving the mount in altitude using the altitude adjusters and in azimuth using the two azimuth adjusters. After that unsync the mount then check your first two alignment stars, if they are significantly off you can replace one or both with the same or another star. The process is really quite simple once you get used to it, if you are having problems it is NOT that your mount in not level, it is something else, most likely not following the procedure correctly. Good Luck!

John. G


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guyroch
Vendor (BackyardEOS)
*****

Reged: 01/22/08

Loc: Under the clouds!
Re: weird issue... new [Re: rmollise]
      #6320333 - 01/18/14 11:56 AM

Quote:

Quote:



I guess I do know a thing or two about geometry after all; sorry to disappoint you!




Maybe you do, maybe you don't. I have no way of knowing. If you do, you haven't thought this through very well.






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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: John608]
      #6320338 - 01/18/14 11:59 AM

Ah thank you. Actually the slope is very slight. Zero chance of tipping over, thankfully. :-)

I am assuming that after I align, I then unsync and can restart the alignment process. Or just slew to and object say m67 and if its off I might need to realign?


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